Computer security is a serious requirement, particularly in computer systems hooked up to a network, whether a local area network or a wide area network. Computers which are connected to the Internet have a particularly great need for a security system. A computer hacker might seek to obtain unauthorized access to a computer to tamper with programs or data or to read data, either as a prank or with the intention of gaining an economic advantage over persons authorized to have access to the computer system. An unauthorized employee might gain such access to confidential information of the employer. Even computers that are not networked can benefit from a security system to protect against unauthorized persons who might gain access to the computer when no one else is around.
Such an intruder might seek to launch a process within the computer, read or copy a file, delete a file, add, delete, or change data in a file, kill a process, introduce a virus or a Trojan horse, or do other mischief. Consequently, it is desirable to have a computer security system.
There exist computer security techniques which restrict access to material in the computer memory on a file by file or directory by directory basis. There also exist computer security techniques that limit access to files on a person by person or group by group basis, and other techniques that permit reading but not writing. However, these existing techniques are limited in their versatility and/or adaptability, for example merely denying access to files, without the ability to take other action.